Balloon catheter stent delivery system with ridges

ABSTRACT

A balloon catheter and stent delivery system for medical treatment of a patient includes a balloon having a pattern of ridges in an initial deflated state. The ridges may cooperate with structural elements of a stent crimped onto the balloon, to increase and enhance longitudinal retention of the stent while the catheter system is advanced or withdrawn. Upon inflation, the balloon recovers to an inflated shape having a cylindrical working portion. The balloon catheter thus provides for uniform expansion of the stent when the balloon is inflated. The present invention also tends to protect the leading or distal end of the stent during advancement, and tends to protect the proximal end of the stent during any withdrawal of the catheter system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of United States Provisional PatentApplication No. 60/269,430 filed Feb. 16, 2001.

BACKGROUND AND SUMMARY OF INVENTION

1. Technical Background

The present invention relates generally to medical devices, and moreparticularly to a balloon catheter and stent delivery system.

2. Discussion

The present invention involves a balloon catheter for inserting a stent,vascular scaffold, or other medical device to a desired site in apatient for medical treatment The balloon is specially shaped withstructural features for cooperating with corresponding stent designs toenhance stent retention.

For purposes of brevity, the following background and description willfocus generally on the example of a medical device delivery system, inwhich the medical device is a stent, and the delivery system is based ona balloon catheter. Of course, other medical devices and other deliverysystems that are within the scope of one of the claims below areincluded in the present invention.

It is desirable to provide a novel combination stent delivery system,along with a unique manufacturing process, having an optimum arrangementof several features. These desirable features include a tendency toretain the stent in position on a deflated balloon, small initial sizeor profile, bending flexibility, column stiffness or pushability, pullstrength, inflation strength (sometimes referred to as “rated burstpressure”), etc.

To provide an optimum arrangement of these features, the presentinvention recognizes and takes advantage of structural aspects ofcertain stents, such that the delivery system optimizes stent retentionwithout compromising any of the other performance qualities.

Among the stent structural features that may be utilized by the presentinvention are an expandable cylindrical mesh or lattice, stents arepreferably designed to be flexible during delivery and bend along avascular path. One design that allows such flexibility is to include aseries of main elements for hoop strength, preferably coupled by aseries of flexible links to enhance flexibility. The stent shouldpreferably also have an optimum selection of features, includingflexibility, small profile, hoop strength when expanded, and resilience,etc.

Accordingly, stent delivery systems of the present invention provideballoons for delivery and expanding the stent, in which the balloon hasa deflated shape with a pattern of ridges or bumps. These ridges orbumps tend to increase stent retention during delivery, and preferablycooperate with the pattern of main stent elements and flexible links, tobetter hold the stent in place on the catheter delivery system.

BACKGROUND

Balloon catheters are used in a variety of therapeutic applications,including intravascular catheters for procedures such as angioplastytreating coronary, neurological and peripheral blood vessels partiallyor totally blocked or narrowed by a stenosis. By way of example, thepresent invention will be described in relation to coronary andperipheral angioplasty treatments. However, it should be understood thatthe present invention relates to balloon catheters and stent deliverysystems generally, and is not limited to the specific embodimentsdescribed herein.

Most balloon catheters have a relatively long and flexible tubular shaftdefining one or more passages or lumens, and an inflatable balloonattached near one end of the shaft. This end of the catheter where theballoon is located is customarily referred to as the “distal” end, whilethe other end is called the “proximal” end. The balloon is connected toone of the lumens extending through the shaft to selectively inflate anddeflate the balloon. The other end of this inflation lumen leads to ahub coupling at the other end for connecting the shaft lumens to variousequipment. Examples of this type of balloon catheter are shown in U.S.Pat. No. 5,304,197, entitled “Balloons For Medical Devices AndFabrication Thereof,” issued to Pinchuk et al. on Apr. 19, 1994, andalso in U.S. Pat. No. 5,370,615, entitled “Balloon Catheter ForAngioplasty,” issued to Johnson on Dec. 6, 1994.

A common treatment method for using such a balloon catheter is toadvance the catheter into the body of a patient, by directing thecatheter distal end percutaneously through an incision and along a bodypassage until the balloon is located within the desired site. The term“desired site” refers to the location in the patient's body currentlyselected for treatment by a health care professional. A larger guidingcatheter may often be used to access the local area near the desiredsite, providing a smooth, supported lumen for conducting other devicesincluding balloon catheters to the desired site. After the balloon iswithin the desired site, it can be selectively inflated to press outwardon the body passage at relatively high pressure to a relatively constantdiameter, in the case of an inelastic or non-compliant balloon material.

This outward pressing of a constriction or narrowing at the desired sitein a body passage is intended to re-open or dilate that body passagewayor lumen, increasing its inner diameter or cross-sectional area. Whenperformed in a blood vessel, this procedure is called “angioplasty.” Thenarrowing of the body passageway lumen is called a lesion or stenosis,and may be formed of hard plaque or viscous thrombus. The objective ofthis angioplasty procedure is to treat the lesion by increasing thecross-sectional area of the blood vessel, to encourage greater bloodflow through the newly expanded vessel.

Unfortunately, the lumen at the angioplasty site may re-close or becomenarrow again. This possible phenomenon is called restenosis, and mayoccur in a certain percentage of percutaneous transluminal angioplastypatients. Restenosis may require an additional procedure, such asanother angioplasty, drug therapy treatment, or even surgery includingbypass graft.

Stents:

In an effort to prevent restenosis, a short flexible cylinder orscaffold made of metal or polymers, referred to as a stent, may bepermanently implanted into the vessel to hold the lumen open, toreinforce the vessel wall and improve blood flow. In 1998, coronarystents were placed in an estimated half million patients in the UnitedStates. The presence of a stent tends to successfully keep the bloodvessel open longer, but their use may be limited by various factors,including size and location of the blood vessel, a complicated ortortuous vessel pathway, etc. Also, even a vessel with a stent mayeventually develop restenosis.

One type of stent is expanded to the proper size at the desired sitewithin the lesion by inflating a balloon catheter, referred to as“balloon-expandable” stents. Balloon-expandable stents are crimped orcompressed onto a deflated balloon, to a diameter during delivery thatis smaller than the eventual deployed diameter at the desired site.

However, friction forces during delivery may tend to cause a crimpedstent to slip in a proximal direction while the catheter system isadvanced, or possibly to slip in a distal direction if the physiciandecides to withdraw the stent without deploying it. It is of coursedesirable to retain the stent in the proper position during movement,both advancement along a vascular path to the desired site, as well as,subsequent removal if necessary.

In addition, it is desirable to provide a stent delivery system withgreater stent retention, that is more capable of holding the stent inposition, or also of advancing a crimped stent across a previouslydeployed stent, or possibly withdrawing it into a guiding catheter.

Drug Delivery:

The present invention is preferably used with a stent or other medicaldevice that may be provided with one or more coatings, to achieve evengreater effectiveness. Such coating or coatings may be selected amongvarious coatings, including therapeutic coatings such as anticoagulants,antiproliferatives, or antirestenosis compounds.

For example, a preferred coating for a stent is an anticoagulant coatingsuch as heparin. Another preferred coating is an antirestenosiscompound, such as for example rapamycin (which is also known assirolimus). Such a compound can be very effective at resisting a vesselfrom re-closing. Any particular coating or type of coating may of coursebe used independently or in conjunction with any one or more coatings,as desired.

Some pioneering research in drug-coated stents has been conducted, andis described in the following publications, all of which are assigned toCordis Corporation and are incorporated herein by reference: (i)European Patent Application number EP 99/302918 A2, entitled “Stent WithLocal Rapamycin Delivery” by Wright et al., filed on Apr. 15, 1999, (ii)PCT Patent Application number US0115562, entitled “Delivery Devices ForTreatment Of Vascular Disease” by Falotico et al., filed on May 14,2001; and (iii) PCT Patent Application number US0115564, entitled“Drug/Drug Delivery Systems For The Prevention And Treatment Of VascularDisease” by Falotico et al., filed on Oct. 14, 2001.

Accordingly, it is an object of the present invention to provide ballooncatheter systems for enhanced position retention of a stent or othermedical device during longitudinal movement of the catheter.

It is a further object of the present invention to provide methods formaking balloon catheter systems having enhanced position retention of astent or other medical device.

It is a further object of the present invention to provide methods formaking balloon catheters for enhanced stent position retention.

These and various other objects, advantages and features of theinvention will become apparent from the following description andclaims, when considered in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of a balloon catheter having astent mounted around the balloon, arranged according to the principlesof the present invention;

FIG. 2 is a longitudinal cross-section view of a balloon catheteraccording to the principles of the present invention;

FIG. 3 is a partial cross-section view of a balloon and a correspondingpartial pattern view of a section of a stent;

FIG. 4 is a series of partial longitudinal cross-section views ofballoons according to alternate embodiments of the present invention;

FIG. 5 is a partial longitudinal cross-section view of a stent and aballoon catheter, showing a fully inflated balloon;

FIGS. 6-8 are partial elevation views of a balloon catheter distal endand a stent; and

FIG. 9 is a perspective view of an example of balloon forming equipmentaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiments of the presentinvention is merely illustrative in nature, and as such it does notlimit in any way the present invention, its application, or uses.Numerous modifications may be made by those skilled in the art withoutdeparting from the true spirit and scope of the invention.

The present invention relates to a medical device delivery system havinga balloon that is specially shaped when deflated with a series of ridgesor bumps, for cooperating with corresponding designs of the medicaldevice to enhance position retention of the medical device duringmovement of the system. The present invention may preferably be usedwith a medical device having one or more coatings, such as a therapeuticdrug coating.

Balloon Catheters:

Referring to the drawings, a balloon catheter system is depicted, withone of the preferred embodiments of the present invention being showngenerally at 10. The balloon catheter of FIG. 1 has an inflatableballoon 12, a relatively long and flexible tubular shaft 14, and a hub16. The balloon 12 is affixed to the shaft 14 near a distal end of theshaft 14, and the hub 16 is affixed to the proximal end of the shaft 14.

The shaft 14 defines one or more passages or lumens extending throughthe shaft, at least one of which is an inflation lumen 18 connected tothe balloon 12 for the purpose of selectively inflating and deflatingthe balloon 12. The inflation lumen 18 thus provides fluid communicationbetween the interior of the balloon 12 at the distal end of theinflation lumen 18, and a hub inflation port 20 having a coupling orluer-lock fitting at the proximal end for connecting the inflation lumen18 to a source of pressurized inflation fluid (not shown) in theconventional manner.

In the illustrated embodiment, the shaft 14 is constructed of an innerand outer tubular body 22 and 24. The inner body 22 defines a guidewirelumen 26, while the inflation lumen 18 is defined by the annular spacebetween the inner and outer tubular bodies 22 and 24. The guidewirelumen 26 is adapted to receive an elongated flexible guidewire 28 in asliding fashion, such that the guidewire 28 and catheter 10 may beadvanced or withdrawn independently, or the catheter 10 may be guidedalong a path selected with the guidewire 28. The shaft 14 may of coursehave various configurations instead of this coaxial design, including asingle extruded tube defining any suitable number of parallelside-by-side lumens, or a proximal shaft portion formed of a metalhypotube connected to a polymer distal shaft portion or other designs.Moreover, the catheter shaft may have a rapid exchange configuration, inwhich the guidewire exits the shaft at a proximal guidewire port locatedbetween the balloon and the hub.

The proximal hub 16 is affixed to the proximal end of the shaft 14, andpreferably provides an inflation port 20 and a guidewire port 30, againwith a luer-lock fitting or hemostatic valve (not shown). Such a valveallows the guidewire 28 to traverse and slide within the guidewire lumen26, yet while resisting the loss of blood or other fluids through theguidewire lumen 26 and guidewire port 30.

As shown in the drawings, the inner and outer tubular bodies 22 and 24are securely received within the hub 16, and surrounded by a tubularstrain relief 32. The hub 16 provides fluid communication between theguidewire lumen 26 and a guidewire port 30 as well as between theannular inflation lumen 18 and the inflation port 20 and coupling.

As shown in the drawings, in particular FIG. 5, the balloon 12 in itsfully inflated profile shape has a cylindrical working portion 36 withan inflated diameter located between a pair of conical end portions 38,and a pair of proximal and distal legs 40 and 42 affixed to the shaft14. In its deflated shape, the balloon 12 preferably has several pleatsthat are wrapped around the shaft. The balloon pleats are illustrated inFIGS. 1 and 6-8 in diagrammatic fashion, but are omitted from the otherdrawings for the sake of clarity.

Radiopaque markers may be used to indicate the position(s) of certaincomponents or features on an x-ray video fluoroscope. For example,marker bands 68 may be attached to the inner body 22 as shown in FIG. 5,to indicate the positions of the proximal and distal ends of a stent 34.

Various materials for balloon catheter components are well known. Forexample, the balloon material is preferably substantially inelastic, andas such it stretches a relatively small amount under pressures of up to15 atmospheres or more. Different balloon materials may be used,including nylon, PEEK, polymer materials sold under the trade name Pebaxor Plexar, polyethylene, HDPE, polyurethane, or a block copolymerthereof. Likewise, various materials may be used for the shaftcomponents and strain relief, including for example all of the materialslisted above, as well as others including metal such as a stainlesssteel hypotube for example. The hub may be made of a hard plastic, suchas for example polycarbonate. Markers 68 may be made of any suitablyradiopaque material, metal, alloy, or combination of materials,including for example tungsten or platinum.

Also, various material structures may be used for any of the components,including for example multilayer structures such as two layers withdifferent properties, or reinforced or braided structures.

Stents and Other Medical Devices:

A stent of any suitable type or configuration may be provided with acatheter 10 of the present invention. Preferably, stents for the presentinvention should have an optimum selection of various features,including among others: a generally cylindrical shape, small initialdiameter, large deployed diameter, flexibility, high hoop strength whendeployed, closed cell construction, and certain other desirableperformance characteristics common to balloon-expandable stents. Anystent design having the desired characteristics may be used with thepresent invention.

Various kinds and types of stents are available in the market, and somedifferent currently available stents are acceptable for use in thepresent invention, as well as new stents which may be developed in thefuture. The stent 34 depicted in the drawings is a cylindrical metalmesh stent having an initial crimped outer diameter, which may beforcibly expanded by the balloon to a deployed diameter. When deployedin a body passageway of a patient, the stent may be designed topreferably press radially outward to hold the passageway open.

An example of a stent with a preferred combination of features is knownas the Bx Velocity, available from Cordis Corporation in Miami, Fla. TheBx Velocity stent has an advantageous arrangement illustrated in FIG. 3,including an alternating series of structural elements for strength andflexible link for flexibility. Of course, the present invention may beused with any stent having a suitable configuration.

Among the stent structural features that may be included in such asuitable configuration are an expandable cylindrical mesh or lattice,designed to be flexible and bend along a vascular path. An example of apossible design having these features may include a series of mainstructural elements 64 for hoop strength, coupled by a series offlexible links 66 to enhance flexibility.

The present invention may be used with any other medical device havingthe requisite features, and which is delivered by a catheter deliverysystem with the claimed elements.

Preferably, the stent or other medical device may be provided with oneor more coatings. Such coating or coatings may be selected among variouscoatings, including therapeutic coatings such as anticoagulants,antiproliferatives, or antirestenosis compounds.

For example, a preferred coating for a stent is an anticoagulant coatingsuch as heparin. Another preferred coating is an anti-restenosiscompound, such as for example rapamycin (which is also known assirolimus). Such a compound can be very effective at resisting a vesselfrom re-closing. Any particular coating or type of coating may of coursebe used independently or in conjunction with any one or more coatings,as desired.

Because the stent is most often or most likely to be made of metal, forexample stainless steel or nitinol, it is preferable that a coating beapplied with or used in conjunction with one or more polymers. Forexample, an initial polymer coating may preferably be applied to thestent. The therapeutic compound may be applied directly or may beembedded in another polymer coating, as desired.

The balloon catheter may be used for inserting a stent, vascularscaffold or other medical device to a desired site in a patient formedical treatment, in which the balloon is specially shaped withstructural features for cooperating with corresponding designs of themedical device to enhance position retention.

An optimum combination of features for the device and delivery systeminclude a small initial size or profile, bending flexibility, columnstiffness or pushability, pull strength, inflation strength (sometimesreferred to as “burst pressure”), and a tendency to retain the stent inposition on a deflated balloon.

To provide an optimum arrangement of these features, the presentinvention recognizes and takes advantage of structural aspects ofcertain stents, such that the delivery system optimizes stent retentionwhile maintaining the performance qualities.

Ridges or Bumps:

Accordingly, medical device delivery systems of the present inventionprovide balloons with a deflated shape having a pattern of radiallyextending ridges 50. These ridges 50 preferably cooperate with thepattern of main structural elements and flexible links, to hold thestent in place on the catheter delivery system.

A novel balloon catheter system of the present invention providesseveral advantages. Among these advantages is that the balloon in aninitial deflated state has a series of ridges or bumps for cooperatingwith the structure of the selected stent, to enhance stent positionretention. This improved stent retention results from crimping a stentaround a previously formed balloon having the ridges of the presentinvention. After crimping, the circumferential ridges formed on theballoon increase stent retention of the delivery system. In thecurrently preferred embodiment as shown in FIG. 3, the ridges 54 andvalleys 52 of the deflated balloon 12 are preferably aligned with acorresponding series of structural stent elements.

Such alignment of the balloon ridges and the stent structural elementspreferably involves sizing and positioning each ridge within andsurrounded by a corresponding generally cylindrical stent structuralelement. In other words, as illustrated in FIG. 3, each structuralelement portion of the stent pattern is preferably arranged to match andbe crimped around a corresponding ridge formed on the balloon. Theremaining portions of the stent pattern between structural elements,preferably flexible linkages of some kind, should match and be crimpedaround the remaining portions of the balloon between ridges.

Of course, the inverse arrangement is also within the scope of thepresent invention in which the structural elements of the stent arealigned between, rather than aligned with, the balloon ridges.

In general, the present invention relates preferably to a stent having arepeating serial pattern, aligned and arranged with a correspondingrepeating pattern of shaped features or ridges formed on a deflated,pleated and wrapped balloon on a catheter.

The balloon pattern of shaped features or ridges may also have variousshapes, examples of which are shown in FIGS. 4 a-c. The size and shapeof the balloon ridges or bumps may be varied to suit preferences, or tooptimally accommodate various designs of the stent or of the medicaldevice. FIG. 4 a for example shows a balloon having valleys 56 andelliptical ridges 58. FIG. 4 b shows a balloon having adjacent roundedlobes 60. FIG. 4 c shows a balloon having an undulating or sinusoidalseries of shapes 62.

In addition, the balloon preferably defines a pair of shoulders 44 and46 in the initial deflated shape, proximal and distal of the stent, tofurther enhance the tendency of the stent to maintain position on theballoon, as well as providing a smooth and gentle surface duringadvancement and possible retraction of the stent into position. Thiscoordinated design of the balloon and stent optimizes many of thedesired performance features of the stent delivery system in general,and increases stent retention in particular.

These preferably curved annular shoulders immediately adjacent theproximal and distal ends of the stent should have a diameter equal to orgreater than the crimped stent, thus protecting the stent and minimizingany possibility of the stent moving due to friction. The shoulders andtransition portions may also tend to act as dilators, to encourage easyadvancement through challenging anatomy or a previously deployed stent,or withdrawal into the guiding catheter. The proximal and distalshoulders may be of any desirable shape, with preferably an outerdimension greater than the crimped stent.

Accordingly, the balloon also has a composite profile shape which variesat different pressures. The balloon initially is in a deflated state andhas a deflated profile shape, as specifically illustrated in FIG. 2,having a central bed portion with a deflated bed diameter being flankedby a pair of proximal and distal shoulders 44 and 46 defining deflatedshoulder diameters that are preferably larger than the deflated beddiameter.

The balloon shoulders taper smoothly down to proximal and distalcylindrical balloon leg 40 and 42. The proximal balloon leg 40 isaffixed to the outer tube 24, while the distal balloon leg 42 is affixedto the inner tube 22. This deflated balloon profile shape thus providesa bed or nest portion for receiving the stent 34 and tending to hold thestent 34 in place, while minimizing friction or adverse contact betweenthe ends of the stent 34 and a blood vessel wall. The present inventionthus tends to protect the leading or distal ends of the stent 34 duringadvancement into the patient's body, and the proximal end of the stent34 during any withdrawal of the catheter system.

FIG. 5 depicts the balloon 12 in its fully inflated profile shape. Theshoulders and ridge shapes disappear, and the balloon profile shapechanges or morphs into a different profile shape when inflated at fillinflation pressure. This fully inflated shape provides the preferablecylindrical working portion 36, wherein the portion of the balloonsupporting and expanding the stent 34 has an inflated diameter largerthan any other portion of the balloon 12. This feature tends to preventany part of the balloon from expanding excessively, which might causelocal trauma to the blood vessel wall.

In the deflated shape, the balloon is therefore temporarily reformedinto a different shape than what might conventionally result from simplydeflating and pleating a previously known balloon. This temporarilyreformed shape enhances stent position retention, and yet exhibits thepreferable fully inflated shape.

Many modifications can of course be made to the present invention, andmany alternate embodiments of the present invention are possible. Someexamples include forming discrete bumps or any other shapes ofprotrusion, rather than circumferential ridges. Likewise, the ridges orbumps may extend radially outward to differing distances, for example anarrangement of major and minor features. Bumps or features on the sameballoon may have different shapes as well as sizes. It is possible thatballoon bumps or ridges may extend through or among interstices or gapsin the stent, or have an outer dimension greater than and extendingbeyond the outer diameter of the stent.

Another advantage of the present invention is the absence of any type ofphysical collar or other retaining device within the balloon, or on theouter balloon surface, or mounted on the balloon catheter shaft, whichmight undesirably increase the primary and/or secondary profiles of thestent delivery system.

The dimensions that may be preferred for the present invention will ofcourse vary, as the device is sized to a patient's vascular anatomy. Thefollowing dimensions are for example only, and will vary greatlydepending on the patient's anatomy; desired area such as coronaryvascular, endovascular, or esophageal areas. Accordingly, all of thefollowing dimensions are in inches, and represent only an approximateaverage of a preferred range of 100%.

The outer diameters of the inner body may be 0.025, of a proximal ordistal shoulder may be 0.040-0.060, of the base stent bed may be0.030-0.050, and of the bumps or ridges may be 0.035-0.065. Thelongitudinal length of the proximal or distal shoulder may be 0.250, ofthe bumps or ridges may be 0.030-0.045, and of the gap or distancebetween bumps or ridges may be 0.040-0.060.

Of course, the ridges may be made by any suitable method, and may haveany suitable shape and arrangement, in accordance with the scope of thepresent invention. The present invention may be made for example usingany of the following methods, as well as various modifications that willbe apparent to those skilled in the art.

First, a balloon catheter is assembled using generally conventionalmethods of extrusion, injection molding, and adhesive or heat-sealingfor example. Then the balloon is preferably pleated, in which theballoon is folded into any suitable or preferable number of longitudinalpleats. The pleated balloon is preferably heated slightly for a shorttime, to cause the balloon material to accept a “memory” or a preferencefor a pleated configuration when deflated. Of course, the pleating stepmay be conducted in a conventional manner, but the “heat-pleating” stepis preferred. For example, if nylon balloon material is used, theheat-pleating may be performed with a temperature of up to approximately70° C. for up to about half a minute.

The pleated “wings” are then wrapped around a portion of the cathetershaft all in the same direction, either manually or by using a pleatingmachine.

The balloon is then temporarily held in its pleated condition byslipping a forming tube in the proximal direction onto the pleatedballoon, while the assembly is transported to the next processingstation. The balloon is heated, preferably at 60-80° C. for under 30seconds.

The forming tube may then be removed. The folded and pleated balloon isthen placed in a mold 70 to form the desired balloon bumps or ridges. Amold component is shown in FIG. 9, with one possible configurationaccording to the present invention. The mold 70 is used with anidentical and opposing mold, both of which have a series of recesses 72for creating the desired bumps or ridges. A passage is formed throughthe mold 70, to allow the catheter to be inserted within the mold 70.This passage has proximal and distal extensions 76 and 74, and thepassage extends fully through the length of the mold 70. The proximalend of the proximal extension 76 is chamfered, beveled, or angled 78, toallow easy introduction of the balloon into the mold 70. When theballoon is inside the clamped mold 70, it is pressurized and heated fora time. The mold 70 may be made of any suitably heat-resistant and rigidmaterial, including a transparent material such as acrylic. The heat andpressure may preferably be about 80-100° C. and 175-225 psi for abouthalf a minute. The mold 70, which is preferably a pair of “clam-shell”dies having specific shapes formed in their surfaces, are preferablymade of polycarbonate and acrylic inserts, inside a heat-sealingmachine. The mold 70 preferably has a desired series of cylindricaland/or doughnut-shaped cut-outs or recesses 72 formed on the interiorsurface of the mold 70, as illustrated in FIG. 9.

After the pressure is released, the pair of dies which form the mold 70are opened. The resulting balloon catheter assembly thus exhibits thedesirable ridges of the present invention.

A stent is placed over the shaped balloon, such that the stentpreferably has structural elements that align with the balloon ridges.The alignment of the stent in position can be facilitated by one or moremarker bands on the balloon catheter shaft. The resulting assembly maybe placed in a crimping device, which uniformly squeezes the stent ontothe balloon. The stent is then gently crimped or compressed around theballoon, with the pleats, ridges and shoulders intact, to a crimpedcondition in which the stent has a specific crimped outer diameter.

When the balloon is pressurized, a pressurized fluid is applied to theinflation port and through the inflation lumen. The pressure of theinflation within the mold may slightly exceed the rated burst pressureof the balloon, and the mold will prevent expansion of the balloon whileallowing the series of ridges or bumps, and proximal and distal balloonshoulders to form. The pressurized fluid may preferably be dry nitrogen,and the pressure may preferably be maintained for a preselected periodof time.

The mold used during the process described above may be formed as shownin FIG. 9. While the mold with the accompanying balloon catheter is heldunder pressure, they are then held in a hot box or heated die. The heattends to set the balloon in place, thus forming the desired series ofridges or bumps, and proximal and distal shoulders 44 and 46. Of course,a hot air or liquid system may also be used. The preferred temperatureof the heating system is preferably below the permanent deformationtemperature of the balloon material, and the time and pressure of thisprocess may be extended to ensure that such a temperature will result inthe desired composite shape and temporary reformation of the balloon.

The pressure is released and the baloon assembly is then removed fromthe mold and heating system. In the alternative, the system is no longerheated, but the pressure may be maintained as the balloon assembly isallowed to cool for a period of time. The pressure is released, then themold is opened.

Several features of this preferred method of making the balloon catheterstent delivery system of the present invention have an effect on theperformance of the resulting product, including the temperatures,pressures, time periods, crimped outer diameter of the stent, theinternal diameter of the mold, as well as the thermal characteristics ofthe balloon and mold. These characteristics may be optimized andselected to result in a desired combination of performance attributesfor the end product.

It should be understood that an unlimited number of configurations forthe present invention could be realized. The foregoing discussiondescribes merely exemplary embodiments illustrating the principles ofthe present invention, the scope of which is recited in the followingclaims. Those skilled in the art will readily recognize from thedescription, claims, and drawings that numerous changes andmodifications can be made without departing from the spirit and scope ofthe invention.

1. A balloon catheter stent deployment system, comprising: a ballooncatheter with a flexible shaft having proximal and distal ends, a hubaffixed to the shaft proximal end having an inflation port, and aninflatable balloon affixed to the shaft near the shaft distal end; theshaft defining an inflation lumen providing fluid communication of aninflation fluid between the hub inflation port and the balloon; suchthat the balloon is adapted for selective inflation from a deflatedstate to an inflated state, as well as later deflation; the balloon inthe inflated state having a cylindrical working portion located betweena pair of conical portions and a pair of leg portions affixed to theshaft; the balloon being initially in the deflated state having multiplelongitudinal pleats wrapped around a portion of the shaft; an expandabletubular mesh stent defining a tubular wall thickness, mounted around theballoon and being crimped in an initial state to an initial crimpedouter diameter; the stent in the initial state having a relaxedconfiguration with substantially no tendency to self-expand absent anexpansive force caused by inflating the balloon; wherein the balloon inits deflated state defines a series of ridges in a region of the balloonunderneath the crimped stent, and defines a first and second balloonshoulder located immediately proximal and distal of the stent and aballoon bed portion defined between the balloon shoulders, wherein theridges each extend around the entire circumference of the deflatedballoon; each ridge having a constant wall thickness with a convex outersurface and a concave inner surface; thereby tending to fictionallyretain the stent in an initial longitudinal position while the cathetersystem is advanced or withdrawn along a vascular path and; wherein theballoon is adapted to inflate and expand the stent to a larger deployedstent diameter, whereby the balloon assumes substantially the inflatedstate with said cylindrical working portion above a transition pressure;such that the ridges are substantially not present in the inflatedstate; whereby the stent delivery system tends to retain the stent in aninitial longitudinal position while the catheter system is advanced orwithdrawn along a vascular path.
 2. The balloon catheter stentdeployment system of claim 1, wherein said stent is formed of metal. 3.The balloon catheter stein deployment system of claim 1, wherein thestent has a coating.
 4. The balloon catheter stent deployment system ofclaim 3, wherein the coating is loaded with a therapeutic compound ordrug, and is adapted to release it for treatment over time.
 5. Theballoon catheter stent deployment system of claim 1, the stent furthercomprising a repeating series of structural elements and flexible linkswherein the elements and flexible links is aligned with the series ofballoon ridges, to further enhance frictional retention of the stent onthe balloon.
 6. The balloon catheter stent deployment system of claim 1,wherein individual ridges extend radially outward to varying dimensions.7. The balloon catheter stent delivery system of claim 1, wherein thestent has a therapeutic drug-release coating.
 8. The balloon catheterstent deployment system of claim 3, wherein the coating includes thedrug rapamycin.
 9. The balloon catheter stent deployment system of claim3, wherein the coating includes the drugs rapamycin and heparin.
 10. Theballoon catheter stern deployment system of claim 3, wherein the coatingincludes one or more of the group of anticoagulants, protein inhibitors,thrombolytics, and antiproliferitives.
 11. The balloon catheter stentdeployment system of claim 1, the stent further comprising a repeatingseries of structural elements and flexible links.
 12. The ballooncatheter stent deployment system of claim 1, further comprising ahydrophilic coating on at least a portion the stent and balloon.
 13. Aballoon catheter stent delivery system, comprising: a balloon catheterwith a flexible shaft having proximal and distal ends, a hub affixed tothe shaft proximal end having an inflation port, and an inflatableballoon affixed to the shall near the shaft distal end; the shaftdefining an inflation lumen providing fluid communication of aninflation fluid between the hub inflation port and the balloon; whereinthe balloon is formed of a substantially inelastic material; such thatthe balloon is adapted for selective inflation from a deflated state toan inflated state, as well as later deflation; wherein the balloon isinitially in a deflated state having a deflated profile shape; whereinthe balloon in its inflated state has a cylindrical working portion withan inflated diameter located between a pair of conical portions and apair of proximal and distal legs affixed to the shaft; an expandabletubular mesh stent defining a tubular wall thickness, mounted around theballoon and being crimped in an initial state to an initial crimpedouter diameter; the stent having a series of structural elements andflexible links; and wherein the balloon in its initial deflated statedefines a series of ridges in a region underneath the crimped stent;wherein the ridges each extend around the entire circumference of thedeflated balloon; such that the ridges are substantially not present inthe inflated state; each ridge having a constant wall thickness with aconvex outer surface and a concave inner surface; and the series ofridges of the balloon in its initial deflated state being arranged tosubstantially align each one of the series of ridges with one of theseries of stent structural elements or flexible links.
 14. The ballooncatheter of claim 13, wherein the balloon ridges have a shape incross-section that is arcuate.
 15. The balloon catheter of claim 13,wherein the balloon in the deflated shape forms a plurality of foldedpleats, wrapped around the shaft; the pleats tending to expand andunfold in the inflated shape.
 16. The balloon catheter of claim 13,wherein ridges have a shape in cross-section that is elliptical.
 17. Theballoon catheter of claim 13, wherein the stent has a therapeutic drugcoating.
 18. The balloon catheter stent deployment system of claim 1,wherein the stent has an anti-restenosis coating.